1

Trialling compost and green manure

crops on an organic vegetable farm Cockatoo 2017

Page 1 of 14

Comparing the use of compost and green manure crop on an organic vegetable farm at Cockatoo, Victoria

Introduction

The aim of this three-year sustainable agriculture project was to understand how compost and/or green manure

crops, as a source of organic matter could improve the physical structure and hence the fertility of a raised bed

vegetable cropping system on a certified organic farm.

The trial site is situated on a 25ha certified organic

horticulture farm at Cockatoo. The farm is on a west facing

slope that has previously been subjected to considerable

erosional forces with substantial soil being eroded and

deposited across the trial site. The grey silty loam duplex soils

are derived from Silurian/Devonian sediments and have poor

structure with minimal A horizon development.

Approximately 10 hectares of the farm are rotationally

cropped with a wide range of vegetables on an annual basis.

The trial site, due to extensive soil movement and position in

the landscape has resulted in an area that has low fertility

and low production levels.

Organic horticulture practiced on this farm relies on the

development of healthy fertile soils through the use of soil building activities, such as using legume crops, green

manures, sound rotations, additions of compost and mineral fertilisers where appropriate (Knight, 2008).

Soil assessment of the trial site indicated that soil compaction appeared to be a major constraint to production. It

was assessed that the soil required the additions of organic matter through either compost and/or green manure

crops, leading to improved structure and allowing crop roots to access increased moisture, oxygen and nutrients

(Termorshuizen, A.J. et al, 2004).

Trial Design

The 0.1-hectare trial site was divided

into 4 treatments (with 4 replications

per treatment). Each replication was

a 100m long x 1.5m wide trial bed.

There were 16 beds in total.

The cultivated area was prepared

using a chisel plough to loosen soil to

a depth of 400mm and then a rotary

hoe and bed-former was used to

establish the 1.5m wide beds (the bed

former reduced the beds to 1m

width.

Andrew Morris (r) with consultant Chris Alenson

Forming the beds

Page 2 of 14

The A horizon depth in the uncultivated soil was 150-200mm and was defined as a grey silty loam. This was

incorporated into the silty loam B-horizon. Observation of the vegetable beds indicate that the cropping beds were

comprised of both A and B horizons.

The beds were established as set out below:

A. Mineral fertiliser (700kg/ha) + 5t/ha compost (both products applied Oct/Nov each year)

B. Mineral fertiliser (700kg/ha) + Green manure crop (both products applied Oct/Nov each year)

C. Mineral fertiliser (700kg/ha) + 5t/ha Compost + 10t/ha rock dust (compost & mineral fertiliser applied Oct/Nov each year & 1 initial application of rock dust) D. Mineral f fertiliser (700kg/ha) + Control (no additional amendments) (product applied Oct/Nov each year) (The certified organic mineral fertiliser was applied over all plots and the application was based on the initial benchmark soil analysis. The mineral fertiliser had an analysis of N 2.2%, P 4.95%, and K 5.46%. It was applied at the rate of 700kg/ha. This equates to an annual application rate of; N 15.4kg/ha, P 34.65kg/ha, K 38.2kg/ha)

Treatments A B C D A B C D A B C D A B C D

1.5m centres with 1m beds

5t/h

a Co

mpo

st +

10t

/ha

rock

dus

t

(com

post

ann

ually

& in

itia

l

appl

icat

ion

of r

ock

dust

)

Cont

rol (

no a

ddit

iona

l

amen

dmen

ts)

100m

Length

Trial Site Layout

Mineral ferti l i ser (700kg/ha) was a lso appl ied to a l l beds on an annual bas is

5t/h

a co

mpo

st (

annu

ally

)

Gre

en m

anur

e cr

op (

annu

ally

)

5t/h

a Co

mpo

st +

10t

/ha

rock

dus

t

(com

post

ann

ually

& in

itia

l

appl

icat

ion

of r

ock

dust

)

Cont

rol (

no a

ddit

iona

l

amen

dmen

ts)

5t/h

a co

mpo

st (

annu

ally

)

Gre

en m

anur

e cr

op (

annu

ally

)

North

5t/h

a co

mpo

st (

annu

ally

)

Gre

en m

anur

e cr

op (

annu

ally

)

5t/h

a Co

mpo

st +

10t

/ha

rock

dus

t

(com

post

ann

ually

& in

itia

l

appl

icat

ion

of r

ock

dust

)

Cont

rol (

no a

ddit

iona

l

amen

dmen

ts)

5t/h

a co

mpo

st (

annu

ally

)

Gre

en m

anur

e cr

op (

annu

ally

)

5t/h

a Co

mpo

st +

10t

/ha

rock

dus

t

(com

post

ann

ually

& in

itia

l

appl

icat

ion

of r

ock

dust

)

Cont

rol (

no a

ddit

iona

l

amen

dmen

ts)

Layout of the trial site

Page 3 of 14

Treatment A - Mineral fertiliser + 5t/ha compost (annually)

The commercial mineral fertiliser was applied annually at the rate of 700kg/ha along with annual applications of

compost at the rate of 5t/ha.

Treatment B - Mineral fertiliser + Green manure crop (annually) - Due to very wet conditions the sowing of a green

manure crop by machinery could not be undertaken so organic Lucerne hay was spread annually across the

appropriate trial beds after application of the mineral fertiliser. This was then incorporated into the soil. The organic

Lucerne hay was spread at a quantity consistent with a sown green manure crop that is grown and then

incorporated into the soil. (7500kg/DM/Ha). The commercial mineral fertiliser was applied annually at the rate of

700kg/ha.

Treatment C - Mineral fertiliser + 5t/ha Compost + 10t/ha rock dust (compost annually & initial application of rock

dust) - The intention behind the treatments utilising compost + rock dust was to investigate the use of a rock dust

(RIRDC, 2001, Van Straaten, 2006) as a source of additional elements allowable under National Organic Standards

(2016). Applied with compost, which potentially provided the opportunity for Humic acids in the compost to assist in

mobilising otherwise tightly bound elements in the rock dust. The commercial mineral fertiliser was applied annually

at the rate of 700kg/ha

Treatment D - Mineral fertiliser + Control The 4 replicated control beds had annual applications of 700kg/ha of the mineral fertiliser, which was the same as

the other treatments. No other amendments were added.

The Lucerne was spread manually on the correct beds

and then incorporated into the soil with a rotary hoe.

Page 4 of 14

Comment on the analysis of the compost used

Compost from a commercial composter is one of the allowable inputs (after confirmation of an acceptable analysis by the

certification agency), that can be utilised in organic agriculture. The compost analysis from the three (annual) deliveries

varied significantly which is not uncommon as ingredients can change from batch to batch and the composting

process itself can vary according to production conditions at the time.

The Carbon to Nitrogen (C:N) ratio is one of the important indicators of the quality of a compost. A mature compost

should have a C:N ratio of less than 15:1. As the C:N ratio becomes wider the availability of N reduces significantly.

Analysis of key nutrients in the 3 annual deliveries is tabulated below and the variation is evident. The first delivery of

compost had an analysis of 0.62% N which equates to 6.2kg of N per tonne, but with a C:N ratio of 36:1 research has

indicated that no N will be released from the compost in the first year and it is likely that N will be drawn from the soil

in an effort to stabilise the high carbon levels (Prasad, 2009).

Compost analysis

2014 2015 2016

Nitrogen 0.62% 1.11% 0.84%

Phosphorus 0.15% 0.60% 0.27%

Potassium 0.33% 0.59% 0.65%

Sulphur 0.15% 0.10% 0.15%

Carbon 22.40% 26.10% 23.70%

Calcium 0.90% 2.03% 1.30%

Magnesium 0.22% 0.47% 0.33%

Sodium 0.08% 0.10% 0.15%

pH 7.5 7.3 6.1

Carbon: Nitrogen ratio (desirable 14:1) 36:1 24:1 28:1

Rock dust

Basalt rock dust was obtained from the Jindivick quarry, which is a basaltic dust from Tertiary volcanics (20-40million years

in age). Basalt being a basic igneous rock contains in its mineral assemblage a wide range of elements that offer potential

for remineralising the soil (Chesworth, 1983). The finer the particle size the more surface area that can be exposed to

biological activity and soil acids that might mobilise nutrients from the material. Sizing of the dust indicated that more

than 45% was less than 250 microns and suitable for the intended trial. A number of the trace elements listed in the table

below have now demonstrated their essentiality to healthy plant physiology and development (Pendias, 1984). Some of

the major silicates analysed are listed in the table below:

Silicate analysis of the basaltic rock dust

Na2O MgO Al2O3 SiO2 K2O P2O5 CaO TiO2 V2O5 Cr2O3 MnO Fe2O3 SO3 CO3O4

2.78% 4.79% 13.66% 51.71% 1.45% 0.37% 7.76% 1.99% 0.02% 0.04% 0.17% 11.94% 0.04% 0.06%

Testing Protocols

Benchmark testing and monitoring criteria was based on assessment of the soil’s physical, biological and chemical

characteristics. A full soil analysis was taken at the start of the trial as a benchmark and further full soil analysis were

undertaken on an annual basis. Monthly analysis of Nitrogen, Phosphorus and Potassium was undertaken to

understand how these nutrients might be mobilised during the seasons due to the various treatment protocols. As

Compost was spread manually to

ensure accuracy of placement and

rate. It was then incorporated with

the bed former.

Page 5 of 14

the cycling of nutrients is critical in organic farm management, both temperature and moisture readings were

reported on a monthly basis as these are key drivers of soil biology responses which drives nutrient availability.

In year two labile carbon was analysed as part of the annual full soil analysis. Labile carbon is the readily decomposable fraction of organic matter and is a better indicator of soil quality status than organic matter, as it responds more quickly (either negatively or positively), to management practices (Bending et al, 2000).

In any form of agriculture when soil is cultivated, organic matter can be easily oxidised, and if soil-building practices

such as the use of legumes, green manure crops or compost are not used in the rotation, labile carbon (the soluble

fraction) in the organic matter can be reduced.

Analysis of Results

Physical observations

The Benchmark soil assessment indicated poor soil physical characteristics with most prominent soil constraints

being identified as a lack of soil structure with poor water infiltration and minimal worm activity. Vegetable root

depth was limited and the reduced pore space indicated possible anaerobic conditions not conducive to

microorganisms responsible for nutrient cycling (Pengthamkeerati et al, 2011).

At the conclusion of the trial there was an improvement in soil granulation, water infiltration and root growth in the

green manure treatment and slight improvement in the compost treatment and compost + rock dust treatment.

Soil Moisture Retention

Each month moisture readings were taken to a depth of 150mm with a digital moisture meter, and over the life of

the project, the soils in the green manure treatment held more moisture than the other 3 treatments. However, this

was not consistent over every season. The winter months showed no difference in soil moisture between the

treatments. The green manure crop treatment showed an increase in soil moisture of 34%, in summer an increase of

48%, and in autumn an increase of 44%. This increased moisture was a key factor in providing an environment that is

suitable for microorganisms involved in N cycling. This was

illustrated by higher levels of Nitrate N in the green manure

treatments throughout the season.

Soil Temperature

There was no discernible difference in soil temperature between

any of the treatments over the life of the project.

Page 6 of 14

pH (1:5 water) 6.1 5.67 5.93 6.2 5.85

Olsen P mg/kg 26 31 38 31 20

Colwell P mg/kg 60 74 86 54 68

Morgan K ng/kg 29 76 87 52 43

Total Nitrogen % 0.23 0.25 0.24 0.24 0.24

Organic matter %OM 5.1 5.8 5.6 5.7 5.4

Total Carbon % 2.93 3.34 3.22 3.26 3.11

0.69 (Nov15) 0.56 (Nov15) 0.68 (Nov15) 0.65 (Nov15)

0.65 (Aprl16) 0.63 (Aprl16) 0.66 (Aprl16) 0.63 (Aprl16)

0.69 (May17) 0.39 (May17) 0.36 (May17) 0.47 (May17)

Effective Cation Exchange

Capacity (ECEC) cmol+/Kg6.87 7.17 6.61 7.4 6.33

Ca/Mg ratio 5.7 3.7 4 4.4 4.8

CEC Calcium % 80.6 71.2 72.0 76.0 75.7

CEC Magnesium % 14.1 19.2 18.0 17.4 15.6

CEC Potassium % 2.1 4.3 5.3 2.7 2.8

CEC Sodium - ESP % 2.1 2.5 1.7 2.0 3.0

Solvita (1 to 5) 2 2.5 3 2.5 2.5

Labile carbon %

Soil Test Key Points

Nutrient Benchmark

03/06/2014

Compost

05/06/2017

Green manure

05/06/2017

Compost/Rock dust

05/06/2017Control 05/06/2017

Soil analysis

The soil pH did not vary significantly between the treatments, and although moderately acid, is not considered

sufficient to impact nutrient availability.

Phosphorus Olsen P (available P) levels in the control were 20mg/kg (desirable 20mg/kg) and Colwell P (which

measures the potentially available P) was 68mg/kg (desirable 45mg/kg). At the end of the trial an increase in the

Olsen P of more than 50% was seen across all treatments compared to the control. Available potassium was

43mg/kg in the Control and 86mg/kg in the green manure bed. Nitrate nitrogen levels monitored on a monthly basis

are discussed below. Total nitrogen did not vary between the controls and treatments.

Organic matter increased across all treatments, with the beds where compost was applied registering the highest

levels. The compost treatments also registered the highest Effective Cation Exchange Capacity (ECEC) levels.

Labile carbon decreased in the Control treatment over the period of the trial indicating that this easily decomposable

fraction of organic matter was cycling but not being replaced. Interestingly in the compost treatment, labile carbon

remained constant, indicating labile carbon that may have been oxidised during cultivation and production, had

possibly been replaced by the addition of the compost. In the green manure treatment, labile carbon increased from

2015-2016 but decreased markedly at the conclusion of the trial. In both the green manure treatment and the

compost+ rock dust treatment, over-cultivation and exposure to the atmosphere over a period of weeks may have

impacted organic matter, thereby oxidising and lowering the labile carbon fraction. The labile carbon in the compost

treatment did not show the same decline. This is hard to explain but could relate to cultivation practices and timing

of cultivation in the specific beds.

Soil moisture meter

Page 7 of 14

Monthly soil analysis

The monthly monitoring of nitrogen, phosphorus and potassium provided particularly interesting results. The

concept behind the monthly monitoring was to understand and perhaps demonstrate how the nutrients N, P & K

might be released due to biological activity during seasonal changes in temperature, moisture and soil oxygen

indicating an environment suitable for these aerobic microorganisms. Prior to the planting of vegetables each season

the commercial mineral fertiliser was applied to all beds. This should be considered when interpreting the results.

Nitrate N

Results for nitrate nitrogen correlated well with soil temperature (seasonal conditions) and moisture. The highest

levels of nitrate nitrogen were seen in the treatments with the green manure crop (Lucerne). The movement of

nitrate nitrogen is a clear illustration of the operation of the nitrogen cycle which is optimised when temperature,

moisture and oxygen along with an organic food source is available to soil microbial life.

The increased soil nitrate nitrogen levels in the green manure treatment over the most productive part of the season

(October-March) has demonstrated that there would be potential to reduce the applications of nitrogen fertiliser

under some vegetable crops, as the levels required were more than adequately supplied by the addition of the green

manure crop. This is displayed below.

Nitrate Nitrogen levels in Treatment 2 (green manure) and nitrogen removal from two vegetable crops

Oct-16 Nov-16 Dec-16 Jan-17 Feb-17 Mar-17 Ave Oct-Mar

Nitrate Nitrogen mg/kg 22 100 88 84 224 181 116

Nitrogen Kg/hectare* 31 140 123 118 314 253 163

Cauliflower nutrient N removal kg/ha 109 109 109 109 109 109 109

Lettuce nutrient removal N kg/ha 120 120 120 120 120 120 120

Source: Understanding nitrogen fertilisers for vegetable production on sands, Sustainable Agriculture Fact Sheet No 4.

*Note: calculation is based on mass of soil in 1ha = 10,000m2 x soil depth of 100mm = 10,000 x 0.1m = 1000m3 Mass by the bulk density 1000 cubic metres x 1.4 ton/m3 (bulk density) = 1400tons x mg/kg nitrate nitrogen

Page 8 of 14

Ammonium N

Ammonium nitrogen is an indication of the progress of decomposition. Organic matter is initially consumed by

microorganisms and is converted to ammonium nitrogen and as temperature continues to increase, the ammonium

nitrogen produced through biological activity is converted to nitrate nitrogen. The graph shows the movement of

ammonium nitrogen through the year according to inputs and seasonal variability.

Phosphorus

The graph illustrating phosphorus levels over the trial period indicate an increase from a base of 25mg/kg to

38mg/kg in the green manure treatment and 30mg/kg in the compost treatments. There was an increasing trend in

the levels of P for all treatments compared to the control.

15

20

25

30

35

40

45

50

Ph

osp

ho

rus

P (

Ols

en)

Phosphorus Levels by Date

Compost Green Manure Compost RD Control

Page 9 of 14

Potassium

The graph illustrating potassium indicates peaks in the compost treatments where incorporation into the soil and

subsequent decomposition has released bound potassium. As an essential major plant nutrient it is readily released

and available from compost. These silty loam soils are relatively low in potassium so additional supplies from

compost are very beneficial. The graph also illustrates that the green manure crop (Lucerne) is also undergoing

decomposition and releasing potassium.

Solvita soil health test (CO2 respiration)

At the conclusion of the trial Solvita tests were undertaken on all treatments. The control, compost and compost + rock dust all indicated 2.5 out of a possible 5. The green manure treatment indicated 3. A score of 2.5-3 is classed as having medium soil activity. It should be noted that soil temperatures at the time of sampling would impact heavily on microbial activity in the soil thus influencing these Solvita tests.

Page 10 of 14

Vegetable yield and quality

The beds containing the green manure crops had the highest production and were higher quality than other

treatments. The colour of the leaves of silver beet were more intense green with a gloss not exhibited on other

treatments. Andrew Morris (farm owner) commented that, “The broccoli plants were healthier; their heads now

coming through in the green manure beds are bigger, far and away bigger than any others. Beans cropped heavier,

silver beet leaves were glossy and all vegetables grown looked healthier”.

Compost beds exhibited the next best production and quality.

Treatment A Treatment B Treatment C Treatment D

Treatment A Treatment B Treatment C Treatment D

Treatment B (Green Manure) is exhibiting larger, glossier and deeper green leaves when compared to the other treatments. There is slight yellow colouring

in Treatments A, C and D

Page 11 of 14

Financial analysis

As a result of improved soil fertility in the green manure bed it is anticipated that 75% less commercial fertiliser

could be used saving at least $475. As plant requirements for Nitrogen are easily being met, there may only be the

need to apply some minor and trace elements to ensure optimum production.

Andrew Morris (Farm owner) said "the improvement in soil fertility resulted in an extra 30 boxes of broccoli being

produced providing an additional return of $900/ha. Broccoli heads that normally weigh in at 150-200grams were

reported in the green manure strips to be at least 250 grams. In addition, the workability of the beds have improved

resulting in energy efficiencies in terms of fuel used.

Annual Costs & Returns

Treatment

A Treatment

B Treatment

C Treatment

D

Commercial Fertiliser 700kg/ha + spread est. $40t $664 $664 $664 $664

Compost 5t/ha = 10m3/ha @ est. $60m3 spread $600 $600

Rock Dust 10t/ha (initial application) est. $75t spread $750

Green Manure seed & sowing est. $230ha $230

TOTAL $1264 $894 $2214 $664

Potential fertiliser saving $475

Or profit from additional yield if status quo continued $900

The 2 treatments with compost applications did not show a significant increase in yield or quality. However, there

will be some benefits from the addition of mineral elements contained in the compost. There are also residual

benefits that may have accrued due to the increases in organic matter and organic carbon.

The cost of supply, delivery and spreading of the compost @ 5t/Ha (calculated at 10m3/ha) was estimated at $60m3.

The value of the nutrients contained in the compost are displayed in the table below.

Value of nutrients in Compost spread at 5t/ha annually over 3 years (15t x $127.85 = $1917.75)

Nutrient

kg/tonne

compost

(2014)

kg/tonne

compost

(2015)

kg/tonne

compost

(2016)

$/kg *

$/tonne

compost

(2014)

$/tonne

compost (2015)

$/tonne

compost (2016)

Total $/tonne

compost 3

years)

Nitrogen 6.2 11.1 8.4 1.27$ 7.87$ 14.10$ 10.67$ 32.64$

Phosphorus 1.5 6 2.7 4.40$ 6.60$ 26.40$ 11.88$ 44.88$

Potassium 3.3 5.9 6.5 1.68$ 5.54$ 9.91$ 10.92$ 26.38$

Calcium 9 20.3 13 0.50$ 4.50$ 10.15$ 6.50$ 21.15$

Sulphur 1.5 1 1.5 0.70$ 1.05$ 0.70$ 1.05$ 2.80$

TOTAL 25.57$ 61.26$ 41.02$ 127.85$

$ Value of Nutrients in 1t of Compost

* based on March 2010 fertiliser prices, calculating the $/tonne by the % nutrient/tonne.

Page 12 of 14

Cost of spreading Lucerne

Due to very wet conditions the sowing of a green manure crop by machinery could not be undertaken so organic

Lucerne hay was spread annually across the appropriate trial beds. This was then incorporated into the soil. The

organic Lucerne hay was spread at a quantity consistent with a sown green manure crop that is grown and then

incorporated into the soil at 7,500kg/DM/Ha. The value of the nutrients are displayed in the table on the following

page and are consistent with the level of nutrients returned to the soil through growing and then incorporating a

green manure crop.

Value of nutrients in Lucerne - spread at 7.5t/ha annually over 3 years (22.5t x $202.70 = $4560.75)

Cost of purchasing the Lucerne hay - $250t x 7.5t/ha annually over 3 years ($250 x 22.5t = $5625)

Summary

The benchmark soil assessment, including the physical, biological and chemical parameters indicated that the soil

base had constraints that were reflected in the reduced production of vegetables from the trial area. Soil chemistry

indicated that one of the major constraints could be low nitrogen levels required to drive production. The soil

physical characteristic that was seen as the major constraint to production was the compacted soil impacting soil

oxygen and moisture penetration. This is partly due to the fine silty loam texture and the cultivation (and

incorporation) of the B profile which is lower in organic matter and biological life. This has created an environment

not conducive to microbial life, which is responsible for the cycling of organic matter.

The trial strategy to overcome these constraints through the addition of compost and/or a green manure crop was

demonstrated to be successful in creating soil conditions suitable for the soil biological life. The green manure crop

in particular with the use of Lucerne increased the soil organic matter and the labile carbon levels. It also stimulated

the cycling of organic matter resulting in consistently higher nitrate nitrogen levels. It was noted that long after the

incorporation of this green manure the levels of nitrogen continued to be at a high level. Levels achieved were well

above desirable levels required for a single vegetable crop in a rotation.

Interestingly the labile carbon decreased in both the green manure and the compost + rock dust treatments over the

last few months of the trial despite an overall increase in organic matter. It is considered that this may be a result of

cultivation of these beds with soil being exposed for some time prior to planting.

The use of compost was the next most successful trial treatment with increased organic matter and stable labile

carbon levels. Increased production was evident.

Nutrient

kg/tonne

lucerne

(2014)

kg/tonne

lucerne

(2015) ave

of 2014 &

2016

kg/tonne

lucerne

(2016)

$/kg *

$/tonne

lucerne

(2014)

$/tonne

lucerne

(2015) ave

of 2014 &

2016

$/tonne

lucerne

(2016)

Total $/tonne

lucerne 3 years)

Nitrogen 20.3 21.3 22.3 1.27$ 25.78$ 27.05$ 28.32$ 81.15$

Phosphorus 2.3 2.45 2.6 4.40$ 10.12$ 10.78$ 11.44$ 32.34$

Potassium 9 13.2 17.4 1.68$ 15.12$ 22.18$ 29.23$ 66.53$

Calcium 18.1 12.6 7.1 0.50$ 9.05$ 6.30$ 3.55$ 18.90$

Sulphur 2.5 1.8 1.1 0.70$ 1.75$ 1.26$ 0.77$ 3.78$

TOTAL 61.82$ 67.57$ 73.31$ 202.70$

$ Value of Nutrients in 1t of Lucerne

* based on March 2010 fertiliser prices, calculating the $/tonne by the % nutrient/tonne.

Page 13 of 14

The treatments with the compost + rock dust demonstrated improved physical characteristics with an increase in

organic matter but decreased labile carbon. This possible anomaly has been discussed above as a result of

production strategies that left the soil surface exposed for some time. There did not appear to be any benefit in

increased plant nutrients released from the rock dust. No increase in production was noted over the control

treatment. The decrease in labile carbon is an important observation indicating the benefit of the analysis in

demonstrating the movement as a component of organic matter due to management practices.

Although not new to science the demonstration of the importance of temperature, moisture and oxygen in the

operation of the nitrogen cycle cannot be underestimated.

The use of Lucerne as a green manure was a most successful input into the system and reinforces the importance of

this strategy in an organic farming system in not only adding organic matter and nutrients to the soil system but

stimulating the soil biology to an extent where nitrogen levels suggest that inputs of commercial nitrogen fertilisers

can be reduced or even replaced.

Key learnings from demonstration

Benchmark visual soil assessment identified a lack of soil structure as a major constraint to production

The Lucerne green manure beds improved the soils physical characteristics (structure and moisture holding

capacity)

The Lucerne green manure beds improved the soils chemical characteristics

The vegetables grown in the Lucerne beds yielded higher production and displayed a deeper green colour

The Lucerne green manure initiated a greater response in terms of mobilising nitrate nitrogen

Labile carbon decreased where trial strips had lengthy periods of exposed soil

Monthly monitoring of N,P, K indicated a strong correlation between high nitrate levels, temperature,

moisture, oxygen and a microbial food source

The 3 year trial demonstrated how the nitrogen cycle responded positively to management and organic

inputs

Page 14 of 14

References

Bending, G.D., Putland, C., & Rayns, F., 2000, Changes in microbial community metabolismand labile organic matter fractions as early indicators of the impact of management on soil biological quality, Biol Fertil Soils (2000) 31:78–84

http://compostforsoils.com.au/images/pdf/cropping/pasture_cropping_web.pdf

Coventry, R.J. et al 2001, Rejuvenating soils with Miniplus, RIRDC, No. 01/173

Chesworth,W. et al, 1983, Agricultural Alchemy-Stones into Bread, Episodes, Vol.no.1

Doran JW, Parkin TB. 1994. Defining and assessing soil quality. p. 3-21. In: Doran JW, Coleman DC, Bezdicek DF, Stewart BA, Editors, Defining Soil Quality for a Sustainable Environment. Soil Science Society of America Special Publication 35, ASA-SSSA, Madison, WI.

Knight, 2009, Green manures, HDRA Downloaded from Internet 11/6/2017:

https://www.gardenorganic.org.uk/sites/www.gardenorganic.org.uk/files/resources/international/GreenMan.pdf

Pengthamkeerati, P., Motavalli, P.P., Kremer, R.J. 2011, Soil microbial activity and functional diversity changed by

compaction, poultry litter and cropping in a claypan soil, Applied Soil Ecology, Vol. 48, Issue 1, May, P71-80

Pendias, K. A., & Pendias, H., 1994, Trace elements in soils and plants, CRC Press, Inc. Florida

Prasad, M., Dr., 2009, A literature review on the availability of nitrogen from compost in relation to the nitrate

regulations SI 378 of 2006, EPA Strive Program, 2007-2013

Termorshuizen, A.J. Moolenaar, S.W. Veeken, A.H.M. Blok, W.J. 2004, The Value of Compost, Reviews in Environmental Science and Bio Technology, 3:343-347

Van Straaten, 2006, Farming with rocks and minerals: challenges and opportunities, An. Acad. Bras.

Ciênc. vol.78 no.4 Rio de Janeiro Dec.

This project is supported by Western Port Catchment Landcare Network through funding from the Australian

Government’s National Landcare Program